Process for producing alloy powder material for R-Fe-B permanent magnets and alloy powder for adjusting the composition therefor

Abstract

A process for producing a starting powder material for use in the fabrication of high performance R--Fe--B permanent magnets comprising an R 2 Fe 14 B compound as the principal phase, which is characterized by adding 70% by weight or less of a specified alloy powder for adjusting the composition comprising an R 2 Fe 17 compound to a specified principal phase R--Fe--B alloy powder comprising an R 2 Fe 14 B compound as the principal phase. This process enables production of a starting alloy powder material considerably reduced in contents of the unfavorable B-rich and R-rich phases which impair the magnetic properties of the final magnet, because the starting powder blend allows the B-rich and R-rich compounds in the principal phase alloy powder to react with the R 2 Fe 17 compound being incorporated in the alloy powder for adjusting the composition.

What is claimed is: 
     
       1. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet, characterized by that an alloy powder comprising an R 2  Fe 17  phase for adjusting the composition and containing 50% by atomic or less of R (where R represents at least one selected from rare earth elements inclusive of yttrium) and balance iron (where at least one of cobalt and nickel may be present as a partial substitute for iron) with unavoidable impurities is added to a principal phase alloy powder which comprises an R 2  Fe 14  B phase as the principal phase and containing from 10 to 30% by atomic of R (where R represents at least one of rare earth elements inclusive of yttrium), from 6 to 40% by atomic of boron, and balance iron (where at least one of cobalt and nickel may be present as a partial substitute for iron) with unavoidable impurities. 
     
     
       2. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the alloy powder for adjusting the composition is added to be mixed with the principal phase alloy powder at an amount of 70% by weight or less with respect to the total weight of said starting alloy powder material. 
     
     
       3. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 2, wherein the alloy powder for adjusting the composition is added to be mixed with the principal phase alloy powder at an amount of from 0.1 to 40% by weight with respect to the total weight of said starting alloy powder material. 
     
     
       4. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the content of the element R in the principal phase alloy powder is in the range of from 12 to 20% by atomic. 
     
     
       5. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the content of boron in the principal phase alloy powder is in the range of from 6 to 20% by atomic. 
     
     
       6. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the content of iron in the principal phase alloy powder is in the range of from 30 to 84% by atomic. 
     
     
       7. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 6, wherein the content of iron in the principal phase alloy powder is in the range of from 60 to 82% by atomic. 
     
     
       8. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein cobalt as a partial substitute for iron is incorporated in the principal phase alloy powder at an amount of 10% or less by atomic. 
     
     
       9. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein nickel as a partial substitute for iron is incorporated in the principal phase alloy powder at an amount of 3% or less by atomic. 
     
     
       10. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the amount of iron containing at least one selected from cobalt and nickel as a partial substitute therefor is incorporated in the principal phase alloy powder at an amount of from 17 to 84% by atomic. 
     
     
       11. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the content of the element R in the alloy powder for adjusting the composition is in the range of from 5 to 35% by atomic. 
     
     
       12. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the content of iron in the alloy powder for adjusting the composition is in the range of from 65 to 95% by atomic. 
     
     
       13. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein iron in the alloy powder for adjusting the composition is partially substituted by 6% by atomic of boron. 
     
     
       14. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the principal phase alloy powder and the alloy powder for adjusting the composition are each prepared by an ingot-making and crushing process or a direct reduction diffusion process. 
     
     
       15. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the amount of iron containing boron as a partial substitute therefor is incorporated in the alloy powder for adjusting the composition at an amount of from 59 to 89% by atomic. 
     
     
       16. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein at least one of the powders selected from the group consisting of a principal phase alloy powder and an alloy powder for adjusting the composition containing at least one selected from the group consisting of 3.5% by atomic or less of copper (Cu), 2.5% by atomic or less of sulfur (S), 4.5% by atomic or less of titanium (Ti), 15% by atomic or less of silicon (Si), 9.5% by atomic or less of vanadium (V), 12.5% by atomic or less of niobium (Nb), 10.5% by atomic or less of tantalum (Ta), 8.5% by atomic or less of chromium (Cr), 9.5% by atomic or less of molybdenum (Mo), 7.5% by atomic or less of tungsten (W), 3.5% by atomic or less of manganese (Mn), 19.5% by atomic or less of aluminum (A1), 2.5% by atomic or less of antimony (Sb), 7% by atomic or less of germanium (Ge), 3.5% by atomic or less of tin (Sn), 5.5% by atomic or less of zirconium (Zr), 5.5% by atomic or less of hafnium (Hf), 8.5% by atomic or less of calcium (Ca), 8.5% by atomic or less of magnesium (Mg), 7.0% by atomic or less of strontium (Sr), 7.0 by atomic or less of barium (Ba), and 7.0% by atomic or less of beryllium (Be). 
     
     
       17. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the alloy powder material contains from 12 to 25% by atomic of an element R, from 4 to 10% by atomic of boron (B), from 0.1 to 10% by atomic of cobalt (Co), and from 68 to 80% by atomic of iron (Fe). 
     
     
       18. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 1, wherein the alloy powder material comprises powder particles whose average size is from 2 to 80 μm. 
     
     
       19. A process for producing a starting alloy powder material for fabricating an R--Fe--B permanent magnet as claimed in claim 18 wherein the alloy powder material comprises powder particles whose average size is from 2 to 10 μm.